This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Spire and Cappuccino are two actin organizers that collaborate to induce oocyte polarization in Drosophila. Studies with their mammalian orthologues have demonstrated this signaling link exists between human Spir1 and Fmn2. To better understand how these proteins interact at a molecular level, we crystallized a ~25 kDa region of human Spir1 alone, or in complex with a peptide corresponding to its binding element of Fmn2. High resolution diffraction data will be obtained at APS 24ID-E via NE-CAT.